1. Technical Field of the Invention
The present invention relates to videophones and videophone systems, and, in particular, to a videophone and videophone system suitable for use in performing videophone communication with a different videophone at a communicating party's location in such a manner that data including audio and images is transmitted and received between the videophone and the different videophone at the communicating party.
2. Description of the Related Arts
Among videophones provided in apparatuses such as 3G (third-generation) cellular phone apparatuses, including “FOMA” and “vodafone” models available in Japan, mutual connection has been performed in accordance with the standard 3G-324M established in the 3GPP (Third Generation Partnership Project).
According to the H.245 system message defined in the standard 3G-324M, alternative settings are possible such as an alteration in image frame rate during videophone communication and an alteration in error resilience level (see, for example, Japanese Unexamined Patent Application Publication No. 2004-32589).
On-vehicle videophones are designed so as not to display images while the vehicles are traveling since the displayed images hinder the driving of the vehicles.
However, in normal communication with a videophone, images are always transferred from a different videophone associated with a communicating party.
Accordingly, a problem occurs in that images which are not displayed during communication actually become wasted.
Also, a problem of deterioration in sound quality occurs since, in general, a data-transfer error rate increases while a vehicle provided with the videophone travels.
To eliminate the problem of deterioration in sound quality, it is possible that the error resilience level be raised while the vehicle travels.
However, by simply raising the error resilience level, the bit rate required for error resilience in multiplex data having a fixed bit rate and including audio data, image data, and data for error resilience is increased. Thus, a tradeoff occurs as a bit rate occupied by the audio data relatively increases, thus resulting in deterioration in sound quality.